Preferential relaxation of positively supercoiled DNA by E. coli topoisomerase IV in single-molecule and ensemble measurements

Article Abstract:

Preferential relaxation of positively supercoiled DNA by Escherichia coli topoisomerase IV (topo IV) has been studied using single-molecule and ensemble measurements. The rate of supercoil relaxation by topo IV is orders of magnitude faster than had been thought. One enzyme at each replication fork may be enough. How topo IV can quickly remove (+) supercoils to support DNA replication without relaxing the essential (-) supercoils of the chromosome is explained.

France, Usage, DNA, Biophysics, Catalysis, Isomerases

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The RssB response regulator directly targets sigma(super.S) for degradation by ClpXP

Article Abstract:

The RssB response regulator has been round to target sigma(super.S) for degradation by ClpXP directly. The degradation of sigma(super.S) in vitro was reconstructed using purified components. Results of the study reveal an important mechanism for regulated protein turnover. In this mechanism a unique targeting protein, activity of which is regulated via specific signaling pathways, catalyzes delivery of a specific substrate to a specific protease.

Cellular signal transduction, RNA polymerases, Adenosine triphosphate, ATP, Proteolysis

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Linking nutritional status to gene activation and development

Article Abstract:

Nutritional status and its relationship to gene activation and development is discussed in this perspective article. It is very difficult, even in primitive cells, bacteria for instance, to see how limiting nutrients perturbs the system of metabolic interactions governing the physiological state of the cell. The many changes in the intermediates that can be responsible for adaptive response are hard to sort out. A very simple solution for the bacterium-forming-a-spore situation has been found

Genetic aspects, Bacteria, Spores (Bacteria), Bacterial spores, Nutrition, Gene expression

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